Various materials have been suggested to replace the well known plaster of paris orthopedic bandages that have been almost exclusively used in the preparation of casts for the immobilization and support of parts of the body. Non plaster of paris products which utilize monomers or reactive polymers supported on a carrier, which may be a fabric or foam, have been recently developed in this art. See for Example, U.S. Pat. Nos. 2,853,067; 3,674,021; 3,669,708; 3,656,475; 3,630,194; 3,613,675 and 3,421,501. These products are hardened by means of heat, radiation or chemical catalyzation, to yield a composite structure which generally has the advantage of lighter weight, improved water resistance, improved x-ray transmission, etc. over plaster of paris casts.
The bandage disclosed in U.S. Pat. No. 3,630,194 has been found to have less than desirable initial strength, (hereinafter "green strength"), i.e. it may take as long as one hour to reach acceptable strength at ambient temperature, unless the flexible carrier is a fiberglass fabric, or other low extension, high initial modulus material.
As pointed out in various patents, (see for example U.S. Pat. Nos. 3,787,272; 3,793,686 and 3,686,725) fiber glass fabrics have certain properties which are undesirable in orthopedic bandages. For example, fiberglass fabrics have poor conformability due to the brittleness of the fiber. The patentees suggest that making the fabric from a fiber consisting essentially of very fine, individual filaments having a diameter of no more than 0.00021 inches improves the poor conformability.
The fabrics disclosed in U.S. Pat. Nos. 3,787,272; 3,793,686; and 3,686,725 are knitted fiberglass fabrics. Although these fabrics have adequate conformability, this construction does not give adequate "green strength" with the cast forming composition disclosed in 3,630,194. It is believed that knitted fiberglass fabrics are not suitable for use with said cast forming compositions because of the relatively low T.sub.g of the polymers obtained by polymerizing the monomers defined therein as opposed to the polymers utilized in the other non plaster of paris products of the prior art, e.g. methacrylate polymers.
It has been found that using lighter weight (thinner) woven fiberglass fabrics as the flexible carrier to improve conformability does not provide bandages having adequate "green strength" with the cast forming compositions disclosed in U.S. Pat. No. 3,630,194. It has been found that a certain minimum mass of the flexible carrier is required or it is necessary to wrap the bandage an excessive number of turns around a limb to provide adequate strength during the initial stages of hardening. Additional wrapping is, of course undesirable to the person preparing the cast.
To solve the above noted problems, a woven fiberglass fabric, cut on the bias was used as a carrier for the cast forming monomers described above. This carrier showed some improved conformability after impregnation, and also yielded a product wherein fraying at the edges was reduced as compared to a similar impregnated product based on a straight cut, fiberglass fabric. However, conformability was not as good as desired and the impregnated, bias cut product tended to neck down when being wrapped around the limb of a patient, thus also requiring more turns.
Attempts to improve conformability by using a very open plain or twill weave fiberglass fabric as a carrier were unsuccessful. The fabric could be made but could not be handled without distorting. This fabric, even after impregnation with a monomer or a reactive polymer, quickly became unacceptably distorted when exposed to water to initiate the reaction.
A leno woven fiberglass fabric was also utilized as a carrier, because of its conformability and open weave. Again after impregnation of the fabric with the above defined cast forming composition, the conformability was lost.
The above noted problems are solved by using, as the flexible carrier, the fabric described herein.